Camshaft adjusters are used in internal combustion engines to vary the control timing of the combustion chamber valves, in order to be able to variably shape the phase relation between a crankshaft and a camshaft in a defined angular range between a maximum advanced position and a maximum retarded position. The adaption of the control times to the current load and rotational speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated in a drive train by which torque is transmitted from the crankshaft to the camshaft. This drive train can be formed, for example, as a belt drive, chain drive, or gearwheel drive.
In a hydraulic camshaft adjuster, the driven element and the drive element form one or more pairs of pressure chambers that act in opposite directions and can be pressurized with hydraulic medium. The drive element and the driven element are arranged coaxially. By filling and emptying individual pressure chambers, a relative movement between the drive element and the driven element is generated. The spring causing a rotating effect between the drive element and the driven element forces the drive element in a preferred direction relative to the driven element. This preferred direction can be in the same direction or in the opposite direction relative to the direction of rotation.
One type of hydraulic camshaft adjuster is the vane cell adjuster. The vane cell adjuster has a stator, a rotor, and a drive wheel with external teeth. The rotor is formed as a driven element and can be locked in rotation usually with the camshaft. The drive element includes the stator and the drive wheel. The stator and the drive wheel are locked in rotation with each other or are alternatively formed integrally with each other. The rotor is arranged coaxial to the stator and within the stator. With their vanes extending in the radial direction, the rotor and the stator form oil chambers that act in opposite directions and can be pressurized with oil pressure and allow a relative rotation between the stator and the rotor. The vanes are formed either integrally with the rotor or the stator or arranged as “inserted vanes” in grooves provided for this reason in the rotor or the stator. The vane cell adjusters also have various sealing covers. The stator and the sealing covers are secured with each other by several threaded connections.
Another type of hydraulic camshaft adjuster is the axial piston adjuster. Here, a displacement element is displaced in the axial direction by oil pressure. This displacement element generates a relative rotation between a drive element and a driven element via helical gearing.
Another type of a camshaft adjuster is the electromechanical camshaft adjuster that has a triple-shaft gear (for example, a planetary gear). Here, one of the shafts forms the drive element and a second shaft forms the driven element. Using the third shaft, rotational energy can be fed to the system or discharged from the system by an adjustment device, for example, an electric motor or a brake. There can also be a spring that increases or decreases the relative rotation between the drive element and the driven element.
DE 10 2009 054 048 A1 shows a camshaft adjuster for a belt drive that has a side cover locked in rotation with a screw with the drive element. For the screw, the side cover has internal threading. So that sufficient thread turns of the internal thread can be formed for the screw, the side cover is enlarged in the axial direction in the area of the internal thread. The spring is arranged on the side of the camshaft adjuster away from the camshaft.